Secretion / K+ regulation

Question 1

What is the effect of low urine pH on net secretion of organic acids?

Answer 1

Decreased - more associated form will back-leak into the blood after being secreted

Question 2

What is the effect of low urine pH on net excretion of organic acids?

Answer 2

Less excretion

Question 3

What is the effect of low urine pH on plasma concentration of organic acids?

Answer 3

Increased

Question 4

Why is alkalinizing the urine a good idea in treating aspirin overdose?

Answer 4

Akalinizing the urine will increase secretion

Question 5

What is the equation for ERPF?

Answer 5

ERPF = clearance of PAH C = (U x V) / P U = urine concentration of PAH V = volume of urine collected per min P = plasma concentration of PAH

Question 6

What is the FF in terms of GFR and ERPF?

Answer 6

FF = GFR / ERPF

Question 7

Why do nephron segments upstream of the distal tubule NOT contribute to regulation of potassium balance?

Answer 7

Most of the filtered load is already reabsorbed (it is unregulated)

Question 8

What is the effect of hyperkalemia on aldosterone secretion?

Answer 8

Direct stimulation from adrenal cortex - independent of RAS axis

Question 9

What is the effect of increased plasma potassium on the basolateral Na-K ATPase pump in the late distal tubule?

Answer 9

Stimulation - K enters the tubule cell, flows down its concentration gradient through K channels in luminal membrane

Question 10

What is the effect of aldosterone on the basolateral Na-K ATPase pump in the late distal tubule?

Answer 10

Stimulation - more K is secreted (more Na reabsorbed)

Question 11

What effects does aldosterone have on the collecting ducts?

Answer 11

Increases number of active epithelial sodium channels in collecting ducts - increases reabsorption of Na and increase secretion of K

Question 12

Why do diuretics that inhibit sodium and water reabsorption cause depletion of body potassium?

Answer 12

Blockage of Na/K/2Cl pumps in thick ascending loop - higher flow causes increased K secretion

Question 13

What is the effect of alkalosis on potassium? Does alkalosis cause hypokalemia or hyperkalemia?

Answer 13

1. Stimulates Na/K ATPase on basolateral membrane of principal cells in late distal convoluted tubule and collecting ducts - increased K in principal cells which flows into lumen - secretion 2. Alkalosis causes hypokalemia